The invention relates to a distal femoral cutting apparatus for resecting a distal face of a femur at a preset valgus angle relative to a patient's intramedullary canal prior to implanting the femoral component of a total knee prosthesis.
The invention also relates to a distal femoral jig assembly used for the mentioned distal femoral cutting apparatus.
Knee joint is the biggest and most complicated joint in a human body. Total knee replacement (TKR) is adopted for severely damaged knee joint. As the knee replacement becomes the most popular surgery for severe knee injuries, research related to TKR are attracting more and more attention.
TKR surgery involves implantation of articulating femoral and tibial components to distal femur and proximal tibia, respectively. Since a femur projects distally in an inward manner at a valgus angle relative to the anatomic axis of the human body and a distal face of the femur has a fossa intercondylaris and is not a planar face, the femur must be resected to conform to the size and shape of the respective prosthetic component so as to properly affix to the prosthetic component. The term “valgus angle” means the angle between the axis of the main body and the channel being considered. In the case of the femur, the valgus angle is the angle formed between the anatomic axis of the patient and the longitudinal axis of the femur, and in the case of the jig, the valgus angle means the angle between the axis of the jig and the passages in the jig.
A plurality of instruments and/or jigs for resecting the distal femur have been developed. Many of the instruments include a cutting block that references an intramedullary rod inserted in the intramedullary canal of the femur. However, such instruments usually cannot provide easily adjustable jig assembly to accommodate to different patients. Meanwhile, due to the distal femur has an asymmetrical shape, the design of the instruments for TKR surgery has to take that into consideration and thereby resulting in complicated structures.
US-A-2010/0057088 relates to a distal femoral cutting apparatus which can be used for resecting either the left or right femur. The apparatus has a handle 12, a sword 14, a base cartridge 26 and a face plate 28 connected by mating threaded connectors so that the various parts can be interchanged with similar parts having different physical properties such as angular orientation. In other words, if the surgeon wants to adjust the valgus angle of the apparatus relative to the anatomic axis of the patient, he or she has to change the corresponding parts of the apparatus on the site. For a surgical procedure, it is rather cumbersome.